Conventional pipe couplings for coupling and sealing adjacent ends of two pipe sections include a coupling sleeve or collar with each pipe end extending into a respective end of the coupling sleeve. A gasket is held adjacent each end of the sleeve overlying the pipe section. An annular flange or gland is associated with each gasket and end of the sleeve, and is tightened to draw down the gasket against the pipe end thus sealing the pipe coupling thereto. One pipe coupling is shown in my prior U.S. Pat. No. 6,168,210 and utilizes continuous flanges that are coupled together via bolts spanning the sleeve. The flanges, sleeve ends, and gaskets have particular relationships that affect the seal and allow the coupling to work over a range of pipe sizes to compress the gaskets against the pipe ends as the flanges are drawn towards each other.
While the continuous flange type of pipe coupling is considered to be particularly advantageous, another style of pipe coupling is proposed in which each flange is provided by a split-ring gland that presents spaced apart confronting ends which can be drawn together with a bolt to close down on the associated gasket. As a consequence, it is not necessary to have bolts that span the sleeve, nor cause the glands to move towards each other. Instead, each end of the sleeve can be independently coupled to the respective pipe end.
In order to work over a range of pipe diameters, the split-ring gland is sized such that it circumscribes most of the circumference of the sleeve end and gasket, but not that portion in the gap defined between the spaced apart confronting ends. However, it is important that the gasket not be exposed radially out of that gap as it will then be a source of leakage and/or failure during installation. To that end, the split-ring gland type of pipe coupling includes a bridge plate or “armor” spanning the gap over the gasket and extending into the gland at each end of the armor. The armor is shaped to conform to the arc of the gland and gasket so as to, in effect, define a continuation of the gasket-confronting surface of the gland. Thus, as the gland is closed down, the gasket will shift and seat throughout the combined circumference of the gland and the armor in order to facilitate installation and create the desired seal.
The gasket inserted into the split-ring gland is an annular gasket generally defining an outer circumferential surface facing the split-ring gland, an inner circumferential surface facing the pipe, and outer and inner side surfaces. One such gasket is provided with a generally annular pressure assist slot extending into the body of the gasket with an opening along the inner side surface of the gasket. Any pressurized fluid that may leak from the pipe along the inner side surface is collected into the pressure assist slot through the opening thereof at the inner side surface. The collected pressurized fluid within the pressure assist slot forces the gasket to expand outwardly to produce a better sealing contact with the pipe, the split-ring gland, and the armor.
As the gland is tightened, however, the opening of the pressure assist slot may be clamped down and closed off, thereby blocking flow of pressurized fluid into the pressure assist slot. It has been proposed to include separate vent holes along the inner side surface spaced radially outwardly from the opening of the pressure assist slot and tunneling through the gasket body into communication with an interior portion of the pressure assist slot beyond the opening. Inclusion of such vent holes can present drawbacks both in the use and in the manufacture of the gaskets.